1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor light emitting device, and more particularly to a method of manufacturing a semiconductor light emitting device to improve quality of cleaving planes.
2. Description of the Related Art
A semiconductor light emitting device mainly refers to a laser diode (LD), and to a light emitting diode (LED). A light emergence face of a semiconductor light emitting device needs to be perpendicular to an oscillation layer and the surface of the light emergence face needs to be smooth to lower the operating power and increase power output of the semiconductor light emitting device. When the light emergence face is formed by dry etching, the surface can become damaged and rough thereby causing large loss of light and low reproducibility. On the other hand, loss of light is small in cleaving planes formed by a scribing process. Accordingly, nitride semiconductor light emitting devices usually use cleaving planes as a light emergence face.
A GaN substrate, a sapphire substrate, a SiC substrate, etc. are used for epitaxial growth to form light emitting structures. When using a GaN substrate, lattice constants of the nitride semiconductor layers are generally the same as lattice constants of GaN substrates since nitride semiconductor layers of the same kind as the GaN substrate are grown on the surface of the GaN substrate. Thus, nitride semiconductor layers of high quality can be obtained, and internal stress in the nitride semiconductor layers is largely decreased compared to using substrates of other kinds. Additionally, a GaN substrate has a high heat conductivity compared to a sapphire substrate and thus has an excellent heat dissipating effect, which is a great merit in view of life span and efficiency of semiconductor light emitting devices. Also, the cleaving planes have high optical quality because a GaN substrate is cleaved together with nitride semiconductor layers. When using a GaN substrate, more devices can be obtained from a single substrate since vertical electrodes can be formed on the GaN substrate. However, forming ohmic contact is not easy when forming electrodes on the bottom surface of GaN substrate.
To easily form ohmic contact, a technique forming a roughness pattern on the bottom surface of a GaN substrate has been suggested. However, the roughness pattern on the bottom surface of the GaN substrate causes diffused reflection due to the roughness of the surface and thus the bottom surface of the GaN substrate seems opaque. Generally, to form cleaving planes, a groove is formed on a bottom surface of semiconductor light emitting devices. Then, external force is applied to generate stress in the deepest portion of the groove and the semiconductor light emitting device is cleaved together with a substrate, thereby forming cleaving planes. However, when the GaN substrate is opaque, forming a groove in a precise position becomes difficult and surface roughness of cleaving planes increases.